Use of amidoamines to treat or prevent acanthamoeba and fungal infections

ABSTRACT

The use of amidoamines to treat or prevent infections attributable to  Acanthamoeba  and fungi is described. The amidoamines are highly effective against both  Acanthamoeba  and fungi, and are less toxic to delicate tissues that may become infected with these types of microorganisms (e.g., the cornea).

This application claims priority from International Patent Application No. PCT/US01/44408 filed on Nov. 27, 2001, which claims priority from U.S. Provisional Application Ser. No. 60/257,572, filed on Dec. 20, 2000.

BACKGROUND OF THE INVENTION

The present invention is directed to the use of certain amidoamines to treat or prevent infections attributable to Acanthamoeba, fungi or combinations of these two types of microorganisms. The invention is particularly directed to the use of the amidoamines described herein to treat or prevent infections of the eye, ear, nose or throat. The pharmaceutical compositions and methods of treatment described herein are also useful in the topical treatment of dermatological infections.

The compositions of the present invention are particularly useful in treating or preventing ophthalmic infections, especially infections of the cornea. Infections of the cornea frequently lead to a serious inflammatory condition known as “keratitis”. If such infections are left untreated, or if the selected therapy proves to be ineffective, Acanthamoeba and fungal infections of the cornea can lead to a rapid destruction of corneal tissues and, ultimately a loss of vision in the affected eye(s).

Various types of agents are currently utilized to treat Acanthamoeba infections. The agents utilized include cationic antiseptics, such as chlorhexidine and polyhexamethylene biguanide (“PHMB”); aromatic diamides, such as propamidine isethionate; and aminoglycoside antibiotics, such as neomycin. Of these agents, the cationic antiseptics chlorhexidine and PHMB are generally considered to be the most effective. However, the efficacy of all of these agents in treating Acanthamoeba infections is fairly limited. Some of the agents have a limited ability to eradicate Acanthamoeba, particularly at the low concentrations required to avoid toxicity to the cornea or other affected tissues, while other agents are inherently toxic to tissues, particularly if prolonged therapy of several weeks or months is required to eradicate the infection.

As with Acanthamoeba infections, fungal infections are relatively rare, but are difficult to treat effectively. The difficulty in treating these infections is due to the limited ability of therapeutic agents to eradicate fungi in situ and the toxic effects of most therapeutic agents on the affected tissues or surrounding tissues.

The following publications may be referred to for further background regarding the current therapies for treating Acanthamoeba and fungal infections of the cornea and associated ophthalmic tissues:

-   1. Kosrirukvongs, P., et al., “Treatment of Acanthamoeba keratitis     with chlorhexidine” Ophthalmology, vol. 106 (4), pages 798-802     (1999); -   2. Tien, S. H., et al., “Treatment of Acanthamoeba keratitis     combined with fungal infection with polyhexamethylene biguanide.     Koahsiung J. Med. Sci., vol. 15, pages 665-673 (1999); -   3. Claerhout, I., et al., “Acanthamoeba keratitis: a review” Bull.     Soc. Belge. Ophthalmol., vol. 274, pages 71-82 (1999); -   4. Lindquist, T. D., “Treatment of Acanthamoeba keratitis” Cornea.,     vol. 17 (1), pages 11-16 (1998); -   5. Gatti, S., et al., “In-vitro effectiveness of povidone-iodine on     Acanthamoeba isolates from human cornea” Antimicrob. Agents.     Chemother, vol. 42 (9), pages 2232-2234 (1998); -   6. Murdoch, D., et al., “Acanthamoeba keratitis in New Zealand,     including two cases with in-vivo resistance to polyhexamethylene     biguanide” Aust. N. Z. J. Ophthalmol., vol. 26 (3), pages 231-236     (1998); -   7. Illingworth, C. D., et al., “Acanthamoeba keratitis” Surv.     Ophthalmol, vol. 42 (6), pages 493-508 (1998); -   8. Azuara Blanco, A., et al., “Successful medical treatment of     Acanthamoeba keratitis” International Ophthalmol., vol. 21 (4),     pages 223-227 (1998); -   9. Duguide, I. G., et al., “Outcome of acanthamoeba keratitis     treated with polyhexamethyl biguanide and propamidine” Ophthalmol.,     vol. 104 (10), pages 1587-1592 (1997); -   10. Hargrave, S. L., et al., “Results of a trial of combined     propamidine isethionate and neomycin therapy of acanthamoeba     keratitis—Brolene Study Group” Ophthalmol., vol. 106 (5), pages     952-957 (1999); -   11. Amoils, S. P., et al., “Acanthamoeba keratitis with live     isolates treated with cryosurgery and fluconazole” Am. J.     Ophthalmol., vol. 127 (6), pages 718-720 (1999); -   12. Navarro-Guerrero, J., et al., “Short communications: a case of     bilateral Acanthamoeba keratitis” Farm Hosp., vol. 22 (5), pages     253-255 (1998); -   13. Park, D. H., et al., “The role of topical corticosteroids in the     management of Acanthamoeba keratitis” Cornea., vol. 16 (3), pages     277-283 (1997); -   14. Chung, M. S., et al., “Fungal keratitis after laser in-situ     keratomileusis: a case report” Cornea., vol. 19 (2), pages 236-237     (2000); -   15. Rodriguez-Ares, T., et al., “Acremonium keratitis in a patient     with herpetic neutrotrophic corneal disease” Acta. Ophthalmol.     Scandinavica., vol. 78 (1), pages 107-109 (2000); -   16. Rahman, M. R., et al., “Trial of chlorhexidine gluconate for     fungal corneal ulcers” Ophthalmic Epidemiol., vol. 4 (3), pages     141-149 (1997);

Acanthamoeba is a common soil and water amoeba characterized by a feeding and dividing trophozoite and resistant cyst stage. The organism is an opportunistic pathogen of humans, causing a potentially blinding keratitis most frequently seen in contact lens wearers. The resistance of the cyst stage to most antimicrobial agents makes acanthamoeba keratitis one of the most difficult ocular infections to manage successfully. Although significant advances in the management of acanthamoeba keratitis have been achieved through the use is of polyhexamethylene biguanide and chlorhexidine (0.02% topical application) treatment failures still occur necessitating surgical intervention with penetrating keratoplasty or, ultimately, enucleation.

The above-discussed difficulties in treating ophthalmic infections and associated inflammation attributable to Acanthamoeba and fungi are also seen in the treatment of other tissues infected with these microorganisms. This is particularly true with respect to otic and nasal infections.

In view of the foregoing, there is a need for a more effective means of treating Acanthamoeba and fungal infections. A therapy that provides for more effective eradication of Acanthamoeba and fungi with less potential for toxicity to the infected tissues is particularly needed. The present invention is directed to satisfying these needs.

SUMMARY OF THE INVENTION

The present invention is based on the finding that certain amidoamines are particularly effective in eradicating Acanthamoeba and fungi, but are relatively non-toxic to ophthalmic tissues. Based on this finding, the present inventors have succeeded in providing an improved means for treating infections and associated inflammation attributable to Acanthamoeba and/or fungi.

The pharmaceutical compositions and methods described herein may be utilized in conjunction with the treatment of various types of Acanthamoeba and fungal infections. However, the compositions and methods of the present invention are particularly well-suited for use in treating conditions wherein topical application of the compositions to the affected tissues is possible. The present invention is therefore well suited for topical treatment of ophthalmic, otic and nasal infections, as well as dermatological infections, and is particularly well suited for treating Acanthamoeba keratitis.

The compositions of the present invention contain one or more amidoamines described herein, and a pharmaceutically acceptable vehicle therefor. The compositions may also include additional antimicrobial agents to complement or supplement the activity of the amidoamines.

The amidoamines of the present invention offer several advantages relative to the existing therapies for Acanthamoeba and fungal infections. For example, these compounds have been found to be effective against strains of Acanthamoeba and fungi that are resistant to the current therapeutic agents, such as chlorhexidine. In addition, the amidoamines are effective against Acanthamoeba and fungi at concentrations suitable for the topical treatment of ophthalmic tissues and other delicate tissues. This combination of greater microbiocidal activity in combination with less toxicity is believed to represent a significant advancement, relative to the current therapies for Acanthamoeba and fungal infections.

DESCRIPTION OF PREFERRED EMBODIMENTS

The amidoamines utilized in the present invention comprise one or more compounds of the following formula, or pharmaceutically acceptable salts thereof (e.g., hydrohalide salts):

 R¹—(OCH₂CH₂)_(m)—X—(CH₂)_(n)—Y   (I)

wherein:

-   -   Y is —N(R³)₂ or     -   Z is oxygen or NR⁴;     -   R¹ is C₆-C₁₈ saturated or unsaturated alkyl, alkylaryl, or         alkoxyaryl;     -   m is zero to 16;     -   n is 2 to 16;     -   R², R³, and R⁴ are independently hydrogen, C₁-C₈ saturated or         unsaturated alkyl or hydroxyalkyl, or a pharmaceutically         acceptable salt thereof.

The compounds wherein m is 0 to 5, n is 2 to 4, R² is hydrogen or methyl, R³ is methyl or ethyl, and R⁴ is hydrogen, methyl or hydroxyethyl are particularly preferred, as are the compounds of Table 1, below:

TABLE 1 COMPD. No. R¹ M n X R² Y R³ Z R⁴ 1 C₁₇ 0 3 CONR² H N(R³)₂ CH₃ — — 2 C₁₃ 0 2 CONR² H N(R³)₂ CH₃ — — 3 C₁₃ 0 2 CONR² H N(R³)₂ C₂H₅ — — 4 C₁₃ 0 3 CONR² H N(R³)₂ CH₃ — — 5 C₁₁ 0 3 CONR² H N(R³)₂ CH₃ — — 6 C₁₁ 0 3 CONR² H N(R³)₂ C₂H₅ — — 7 C₁₁ 0 3 CONR² H

— O — 8 C₁₄ 0 2 R²NCO H

— N H 9 C₁₃ 0 3 CONR² H

— N CH₃ 10 C₁₃ 0 3 CONR² CH₃ N(R³)₂ CH₃ — — 11 C₁₃ 0 3 CONR² H

— N C₂H₄OH 12 C₁₂ 5 3 CONR² H N(R³)₂ CH₃ — — 13 C₁₂ 4 2 R²NCO H N(R³)₂ CH₃ — — 14 C₁₂ 0 3 CONR² H N(R³)₂ CH₃ — — 15 C₁₁ 0 3 CONR² CH₃ N(R³)₂ CH₃ — — 16 C₁₁ 0 3 CONR² H

— N C₂H₄OH 17 C₁₃ O 3 CONR² H

— O —

The most preferred amidoamine is Compound No. 4, which is known as N,N-Dimethyl-N′-tetradecanoyl-1,3-propylenediamine or N-[3-(Dimethylamino)propyl]tetradecanamide. This compound may also be referred to as “CAS Number: 45267-19-4”.

Some of the amidoamines utilized in the present invention are available from commercial sources. For example, Compound No. 4 is available as MIRISTOCOR®, myristamidopropyl dimethylamine phosphate, from Hoffman-La Roche Inc., Nutley, N.J. (USA), and as Schercodine M from Scher Chemicals Inc., Clifton, N.J. (USA); Compound No. 5 is available as LEXAMINE® L-13, lauramidopropyl dimethylamine, from Inolex Chemical Company, Philadelphia, Pa. (USA); and Compound No. 1 is available as LEXAMINE® S-13, stearamidopropyl dimethylamine, also from Inolex Chemical Company.

The above-described amidoamines can be synthesized in accordance with known techniques, including those described in U.S. Pat. No. 5,573,726 (Dassanayake, et al.), the entire contents of which are hereby incorporated in the present specification by reference. Examples of general reaction schemes which may be utilized are provided below.

Scheme I

The following reaction scheme may be utilized to synthesize compounds wherein

X is CONR²:

In the foregoing reaction scheme, A is a good leaving group, such as chloride or N-hydroxysuccinimide.

Scheme II

The following reaction scheme may be utilized to synthesize compounds wherein

X is NR²CO

The following article may be referred to for further details concerning the synthesis of the amidoamines of formula (I): Muzyczko, et al., “Fatty Amidoamine Derivatives: N,N-Dimethyl-N-(3-alkylamidopropyl)amines and Their Salts”, Journal of the American Oil Chemists' Society, volume 45, number 11, pages 720-725 (1968).

The amidoamines of formula (I) can be used individually, in combination with one or more other compounds of formula (I), or in combination with other antimicrobial agents. The compounds may, for example, be used in combination with cationic antiseptics, aminoglycoside antibiotics, quinolone antibiotics, oxazolidinone antibiotics or tetracycline. Examples of suitable cationic antiseptics include biguanides, such as chlorhexidine and polyhexamethylene biguanide (“PHMB”), and quaternary-ammonium compounds, such as benzalkonium chloride and polyquaternium-1.

The compositions of the present invention may also contain one or more low molecular weight amino alcohols to further enhance the antimicrobial activity of the compositions. The preferred amino alcohol is 2-amino-2-methyl-propanol (“AMP”). The term “AMP 95” refers to a commercially available solution (Angus Chemical Company, Buffalo Grove, Ill.) that contains 95% pure AMP and 5% water. AMP 95 is the most preferred low molecular weight amino alcohol.

The amount of the amidoamines of formula (I) utilized in the compositions of the present invention will depend on the purpose of the use, e.g., the treatment of an active infection or the prophylactic treatment of tissues to prevent an active infection from developing. The amount utilized will also depend on the particular tissues being treated. For example, lower concentrations will typically be utilized to treat especially sensitive tissues, such as ophthalmic tissues, while somewhat higher concentrations may be utilized to treat less sensitive tissues, such as the skin. The amount of amidoamine utilized will also depend on the presence or absence of other antimicrobial agents in the present compositions. The concentrations determined to be necessary for the above-stated purposes can be functionally described as “an antiinfective amount”, “an antimicrobial effective amount” or variations thereof. The concentrations utilized will generally be in the range of from about 0.00001 to about 0.1 weight/volume percent (w/v %).

The amidoamines of formula (I) may be included in various types of pharmaceutical compositions. The compositions may be aqueous or nonaqueous, but will generally be aqueous. As will be appreciated by those skilled in the art, the compositions may contain a wide variety of ingredients, such as tonicity agents (e.g., sodium chloride or mannitol), surfactants (e.g., polyoxyethylene/polyoxypropylene copolymers, such as Poloxamine™), viscosity adjusting agents (e.g., hydroxypropyl methyl cellulose and other cellulose derivatives) and buffering agents (e.g., borates, citrates, phosphates and carbonates). The inclusion of borate and/or one or more surfactants in the compositions has been found to enhance the overall antimicrobial activity of the compositions. The inclusion of such agents is therefore desirable in most cases.

It has been found that the amidoamines of formula (I) are most active under alkaline conditions. Accordingly, the compositions of the present invention will preferably be formulated to have a pH greater than 7. The ideal pH values for compositions containing specific amidoamines of formula (I) can be determined by means of routine experimentation, but these values will generally be in the range of 7.5 to 8.0.

As will be appreciated by those skilled in the art, ophthalmic compositions intended for direct application to the eye will be formulated so as to have a pH and tonicity which are compatible with the eye. This will normally require a buffer to maintain the pH of the composition at or near physiologic pH (i.e., 7.4) and may require a tonicity agent to bring the osmolality of the composition near to 300 milliosmoles. However, as indicated above, a slightly alkaline pH is preferred in order to maximize the antimicrobial effect of the amidoamines of formula (I).

The compositions of the present inventions are preferably utilized to treat Acanthamoeba and fungal infections by applying the compositions to the affected tissues from a few to several times per day. The amount of composition applied and the frequency of application are dependent on the particular type of tissue being treated and the severity of the infection.

The following examples are presented to further illustrate methods of synthesizing the amidoamines of formula (I), pharmaceutical compositions containing these compounds, and the antimicrobial activity of these compounds relative to Acanthamoeba and fungi.

EXAMPLE 1

Synthesis of Compound No. 4 (N,N-Dimethyl-N′-Tetradecanoyl-1,3-Propylenediamine)

2.0 g. (0.0196 moles) of 3-dimethylaminopropylamine in 40 ml chloroform was added dropwise to an ice cold chloroform solution (50 ml) of myristoyl chloride (4.17 g., 0.0169 moles). After addition, the ice bath was removed and the solution was stirred for 2 hours. A 25 ml aqueous sodium bicarbonate solution was added and stirred for 30 minutes. The organic layer was then washed with 30 ml aqueous sodium bicarbonate/sodium chloride solution and dried with magnesium sulfate. The solution was concentrated in vacuo and the amide was recrystallized in ethyl acetate to yield 3.29 g. (0.0105 moles, 62.3%) of the subject compound.

¹H NMR (200 MHz, CDCL₃): δ6.9 (s, 1H, NH), 3.3 (q, 3H, NHCH ₂), 2.4 (t, 2H, NCH₂), 2.22 (s, 6H, NCH₃), 2.15 (t, 2H, COCH₂), 1.7−1.5 (m, 4H, COCH₂CH ₂ and NHCH₂CH ₂), 1.25 (s, 20H, COCH₂CH₂(CH ₂)₁₀), 0.88 (t, 3H, CH₃). Elemental Analysis: Calculated for C₁₉H₄₀N₂O (312.52): C, 73.02; H, 12.90; N, 8.96. Found: C, 72.96; H, 12.92; N, 8.93.

EXAMPLE 2

The following formulations are examples of aqueous compositions containing the amidoamines of formula (I). The formulations are suitable for topical application to the eye and other tissues.

Ingredient Amount (w/v %) Formulation No. 1 Compound No. 4 0.001 to 0.01 Boric Acid 0.3  Sodium Chloride 0.64 NaOH/HCL q.s. pH 7.8 Purified Water q.s. 100   Formulation No. 2 Compound No. 4  0.005 Sodium Chloride 0.5  Mannitol 2.5  HEPES  0.119 NaOH/HCl q.s. pH 7.0 Purified water q.s. 100   Formulation No. 3 Compound No. 4  0.001 Boric Acid 0.58 Sodium Borate 0.18 Sodium Chloride 0.49 Disodium Edetate 0.05 NaOH/HCl q.s. pH 7.0 Purified water q.s. 100   Formulation No. 4 Compound No. 4  0.0005 AMP 95 0.45 Boric Acid 0.6  Disodium Edetate 0.05 Sodium Chloride 0.1  Sodium Citrate 0.65 Sorbitol 1.2  Tetronic 1304 0.05 NaOH/HCl q.s. pH 7.8 Purified water q.s.     

EXAMPLE 3

The following experiment was conducted to evaluate the activity of the amidoamines of formula (I) against Acanthamoeba.

A 0.1% stock solution of Compound No. 4 was prepared. The compound was dissolved in TRIS buffer¹ by gently heating and swirling. The final pH was adjusted to 7.8 with 1N HCl. The TRIS buffer control showed that growth of Acanthamoeba was not inhibited by the TRIS. To prepare the samples, a 0.1% stock solution of Compound No. 4 was serially diluted in Mueller Hinton Broth (MHB)^(2,3) (BBL) to provide concentrations of 0.01 w/v %, 0.001 w/v %, 0.0001 w/v %, and 0.00001 w/v %, respectively. Solutions containing 0.02 w/v % polyhexamethylene biguanide (PHMP) and 0.1 w/v % chlorhexidine, respectively, were also utilized as controls.

The samples were inoculated with low levels (approximately 3.0×10² organisms/mL) of the test organism. The test organism was Acanthamoeba polyphaga cysts (ATCC 30871) produced 14 days in. PYG and then 14 days in Page's saline, followed by one month of refrigeration. The samples were checked for survivors at 4, 24, and 48 hours post inoculation. The samples were serially diluted in Dey-Engley neutralizing broth (DE) (Difco) and plated in quadruplicate in tissue culture plate wells containing non-nutrient agar overlaid with E. coli. Plates were sealed and incubated for 14 days at 30-35° C. Results were recorded and counts calculated using the Reed and Muench computation. The results are set forth in Table 2 below:

TABLE 2 Dose/Response Data for Compound No. 4 Against Acanthamoeba Number of Surviving Organisms 0.01% 0.001% 0.0001% 0.00001% Time Compound Compound Compound Compound 0.02% 0.1% Organism (Hrs) No. 4 No. 4 No. 4 No. 4 PHMB Chlorhexidine A. polyphaga 0 3.2 × 10² 3.2 × 10² 3.2 × 10² 3.2 × 10² 3.2 × 10² 3.2 × 10² ATCC 4 <10 3.2 × 10² 3.2 × 10³ 3.2 × 10³ <10 <10 30871 24 <10 1.7 × 10¹ 2.1 × 10³ 3.2 × 10³ <10 <10 Cysts 48 <10 <10 2.1 × 10³ 3.2 × 10³ <10 <10 ¹TRIS buffer was made in sterile water as follows: TRIS (12.11 g/L) and NaCl (8 g/L); add 1.0 N HCL to pH 7.8. ²MHB was made in phosphate buffered saline [NaCl (8.3 g/L), sodium phosphate dibasic (2.38 g/L), sodium phosphate monobasic (0.467 g/L), in distilled water]. ³MHB is recommended as the medium of choice by the National Committee for Clinical Laboratory Standards (NCCLS) M7-A5, Vol. 20, No. 2, pg. 10) for susceptibility testing of commonly isolated, rapidly growing organisms.

EXAMPLE 4

The following experiment was conducted to evaluate the activity of the amidoamines of formula (1) against fungi.

A 0.1% stock solution of Compound No. 4 was prepared. The compound was dissolved in TRIS buffer¹ by gently heating and swirling. The final pH was adjusted to 7.8 with 1N HCl. The TRIS buffer control showed that growth of the fungi was not inhibited by the TRIS. To prepare the samples, a 0.1% stock solution of Compound No. 4 was serially diluted in Mueller Hinton Broth (MHB)^(2,3) (BBL) to provide solutions containing Compound No. 4 in concentrations of 0.01 w/v %, 0.001 w/v %, 0.0001 w/v %, and 0.00001 w/v %, respectively. Solutions containing 0.02 w/v % PHMB and 0.1 w/v % chlorhexidine, respectively, were utilized as controls.

The samples were inoculated with low levels (approximately 1.0×10³ organisms/mL) of the test organism. The test organisms included the fungi C. albicans ATCC 10231 and F. solani ATCC 36031. The samples were checked for survivors at 4, 24, and 48 hours post inoculation. The samples were serially diluted in Dey Engley neutralizing broth (DE) (Difco) and plated in duplicate using trypicase soy agar containing 0.07% asolectin and 0.5% Tween 80. The plates were incubated for 5 days at 20-25° C. and plate counts recorded. The results are set forth in Table 3, below.

TABLE 3 Dose/Response Data for Compound No. 4 Against Fungi Number of Surviving Organisms 0.01% 0.001% 0.0001% 0.00001% Time Compound Compound Compound Compound 0.02% 0.1% Organism (Hours) No. 4 No. 4 No. 4 No. 4 PHMB Chlorhexidine C. albicans 0 3.3 × 10³ 3.3 × 10³ 3.3 × 10³ 3.3 × 10³ 3.3 × 10³ 3.3 × 10³ ATCC 4 <1 4.3 × 10¹ 3.2 × 10³ 3.2 × 10³ <1 <1 10231 24 <1 1.0 × 10¹ 1.5 × 10⁴ 2.5 × 10⁴ <1 <1 48 <1 3.4 × 10¹ 1.3 × 10⁵ 1.3 × 10⁵ <1 <1 F. solani 0 4.9 × 10³ 4.9 × 10³ 4.9 × 10³ 4.9 × 10³ 4.9 × 10³ 4.9 × 10³ ATCC 4 <1 1.0 × 10¹ 6.9 × 10³ 5.9 × 10³ <1 <1 36031 24 <1 <1 9.5 × 10³ 1.0 × 10⁴ <1 <1 48 <1 <1 1.6 × 10⁴ 4.8 × 10³ <1 <1 ¹TRIS buffer was made in sterile water as follows TRIS (12.11 g/L) and NaCl (8 g/L); add 1.0 N HCL to pH 7.8. ²MHB was made in phosphate buffered saline [NaCl (8.3 g/L), sodium phosphate dibasic (2.38 g/L), sodium phosphate monobasic (0.467 g/L), in distilled water]. ³MHB is recommended as the medium of choice by the National Committee for Clinical Laboratory Standards (NCCLS) M7-A5, Vol. 20, No. 2, pg. 10) for susceptibility testing of commonly isolated, rapidly growing organisms.

EXAMPLE 5

The following experiment was conducted to determine the minimum cysticidal concentration (“MCC”) of Compound No. 4 against five strains of Acanthamoeba, and compare the MCC values for Compound No. 4 to those for chlorhexidine.

Two different vehicles were utilized to prepare solutions containing Compound No. 4. The first vehicle was the same as the vehicle described in Formulation No. 4 (see Example 2, above), and the second vehicle was a 2 mM TRIS. HCl solution (pH 7.8).

Minimum cysticidal levels of Compound No. 4 for Acanthamoeba keratitis strains was determined as follows. Briefly, 100 μl serial, two-fold dilutions were prepared across the rows of a microtitre plate. Control wells received only diluent. An equal volume of five strains of Acanthamoba cysts were added to the wells and the plates sealed and incubated at 32° C. for 24 hours. Using a multi-channel pipette, the solutions in the wells were removed and replaced with 200 μl of ¼ strength Lactated Ringer's solution and left at room temperature for 15 minutes. The washing procedure was repeated twice more before finally filling the wells with 100 μl of ¼ strength Lactated Ringer's solution containing live E. coli at an O.D.₅₄₀ of 0.2. The plates were then sealed and incubated at 32° C. for up to 7 days. The minimum cysticidal concentration (MCC) was defined as the lowest concentration of antimicrobial solution that resulted in no excystment and trophozoite replication.

The MCC values for Compound No. 4 and chlorhexidine against the five Acanthamoeba strains (NNA cysts) tested are set forth in Table 4, below.

TABLE 4 Minimum Cysticidal Concentration (micrograms/milliliter) Acanthamoeba Acanthamoeba Strain Uni Tap Acanthamoeba Acanthamoeba Acanthamoeba Formulation Strain 1501-3D Water 1501-3D Strain 1501-2g Strain Ros Strain Watson ALDOX in 15.6 15.6 13.0 15.6 31.3 Tris Buffer ALDOX in 22.5 22.5 11.3 15.6 31.3 Vehicle Chlorhexidine 31.3 26.0 52.1 31.25 62.5

EXAMPLE 6

The efficacy of a formulation containing 0.0005% of Compound No. 4 was tested against several species of both yeast and mold. (The formulation tested was OPTI-FREE® Express® Multi-Purpose Disinfecting Solution, which is identical to Formulation No. 4 in Example 2 above, expect that the OPTI-FREE® Express Solution also contains polyquaternium-1 in a concentration of 0.001 w/v %.) The formulation was inoculated to contain approximately 1×10⁶ CFU/ml of the inoculum. Samples were serially diluted in Dey-Engley medium and plated in soybean-casein digest agar containing neutralizers. The plates were incubated and the numbers of survivors were recorded. The average reduction for mold was 2.9-log units and yeasts were reduced by an average of 3.9-log units after 6-hours of exposure to the formulation. The test results are presented in Table 5 below.

TABLE 5 Efficacy Against Fungi—Log Reduction at 6 Hours Average Log Microorganism Reduction SD N Candida parapsilosis 5.00 ±0.0 3 Candida albicans 2 2.19 ±0.7 16  Candida albicans 1* 4.53 ±0.3 3 Penicillium notatum 2.33 ±0.8 3 Paecilomyces lilacinus 2.70 ±0.1 3 Fusarium solani 4.19 ±0.8 9 Curvularia clavata 1.37 ±0.3 3 Aspergillus fumigatus 3.10 ±1.0 3 

1. A method of treating infections attributable to Acanthamoeba, fungi or a combination of Acanthamoeba and fungi, which comprises applying a topical pharmaceutical composition to the affected tissues, said composition comprising an antimicrobial effective amount of a compound of the following formula: R¹—(OCH₂CH₂)_(m)—X—(CH₂)_(n)—Y   (I) wherein:

Y is —N(R³)₂ or

Z is oxygen or NR⁴; R¹ is C₆-C₁₈ saturated or unsaturated alkyl, alkylaryl, or alkoxyaryl; m is zero to 16; n is 2 to 16; R², R³, and R⁴ are independently hydrogen, C₁-C₈ saturated or unsaturated alkyl or hydroxyalkyl, or a pharmaceutically acceptable salt thereof; and a pharmaceutically acceptable vehicle therefor.
 2. A method according to claim 1, wherein n is 2 to 4, and m is 0 to
 5. 3. A method according to claim 2, wherein R² is hydrogen or methyl, and R³ is methyl or ethyl.
 4. A method according to claim 1, wherein R¹ is heptadec-8-enyl, undecyl, undecenyl, dodecyl, tridecyl, tetradecyl, pentadecyl or heptadecyl, R² is hydrogen or methyl, R³ is methyl or ethyl, and R⁴ is hydrogen, methyl or hydroxyethyl.
 5. A method according to claim 1, wherein R¹ is tridecyl, m is 0, n is 3, Y is N(R³)₂ and R³ is methyl.
 6. A method according to claim 1, wherein the composition further comprises an antimicrobial effective amount of a cationic antiseptic.
 7. A method according to claim 6, wherein the cationic antiseptic is selected from the group consisting of chlorhexidine, PHMB and polyquaternium-1.
 8. A method according to claim 1, wherein the composition is applied to ophthalmic tissues.
 9. A method according to claim 1, wherein the composition is applied to ophthalmic tissues to treat an Acanthamoeba infection.
 10. A method according to claim 5, wherein the composition is applied to ophthalmic tissues.
 11. A method according to claim 5, wherein the composition is applied to ophthalmic tissues to treat an Acanthamoeba infection. 